Tap changer



1,641,294 sapt 1927' c. A. ROBERTS TAP CHANGER 2 Sheets-Sheet l ii PIT-Z,

' I 1,641,294 Sept 1927 c. A. ROBERTS TAP CHANGER Filed Au. s. 1925 2 Sheets-Sheet 2 Patented Sept. 6, 1927.

ourrso stares rarer GFHCE.

CLIFFORD A. ROBERTS, OF PITTSBURGH, PENNSYLVANIA, .ASSIGNOB T0 IPITTSIBUBGH TRANSFORMER COMPANY, A GORIPORATION OF PENNSYLVANIA.

Tar oneness.

Application filed August 3. 1925. Serial No. 47,734.

" constructed; easily operated, and which will not hinder the removal of the top of the transformer. Other advantages of this tap changer are good electrical contacts, which will prevent l ocal heating of the conducting parts, and the impossibility of making connections which would cause short circuits or case showing the position of otherwise damage the apparatus.

In the accompanying drawings showing a preferred form of the inventionliig'. l is an elevation of the contact-making and operating mechanism,

l i 2 is an enlarged sectional view of the packing gland shown in Fig. l,

Fig. 3 is a sectional view of a transformer the switch. The secondar coil of the transformer is represented diagrammatically showing the tap connections.

Fig. 4 is a plan view of the switch slab.

Fig. 5 isa plan view of a modified form of switch slab.

In Figs. 3 and shown at 1. The tank contains the transformer core and coils submerged in insulating oil. As these do not pertain to the invention only one set of coils 0, the secondary in this case, is shown diagrammatically. The terminals of the coils are brought out in the usual manner through bushings 2. The tap connecfionsB-S, 4--4, 5--5 and 6-6 are brought to a switch slab 7 constructed of insulating material and suitably supported above the transformer core. Contact clips 3'-3', 4-4', 5'-5' and 6''6' are mounted on the switch slab and connected to the tap connections. Switch blades .8-8 serve to connect corresponding contact clips, and are mounted on a shaft 9 which is journalled in the insulating slab 7 at 21. The shaft 9 is rigidly connected by means of an insulat- 4; the transformer tank is ing piece 10 to a shaft 11, leading through the cover o of the transformer case and havmg fastened to it an arm 12 B T this arm the operator may lift the switch hlades vertically until they have become disengaged from the contact clips. He may then rotate the switch blades until they are vertically above any pair of contact clips. .The arm is depressed to force the switch blades into the contact clips and establish the new con nection. The pin 13 mounted on the arm 1'2; is arranged to fit into holes in a stationary indexing plate it. This serves the purpose of indicatlng to the operator which contacts are connected. The pin 13 is of such a length that the operator must raise the handle vertically enough to disengage the switch blades before he may rotate it to a position above any other pair of contact clips. When the switch. blades are directly above any pair of contacts the pin 13 registers with a hole in the index plate 14, and will permit the switch blades to be lowered. When fully depressed, the latch 12, which is hinged to the arm 12 may be swung downward to the position shown in Figs. 1 and 3; thereby locking the switch blades in place. To prevent tampering, a bolt 15 may be inserted to securely clamp the apparatus in position. The bolt 15 is similar in its action to pin 13, serving to insure an'exact correspondence between the switch blades and the contact clips in case the joints between shafts 9 or 11 and the insulator l0 become loose. A collar 0* is provided on shaft 11 to limit the upward travel of the moving parts.

'A packing gland as shown in detail in Fig. 2 is provided where shaft 11 passes it'll through the transformer cover, The lower down over t e packing nut 16, protecting it from moisture and preventing the accumulation of water which would otherwise tend to gradually seep through the packing material into the transformer oil, renderm it unreliable as an insulator and endangenng the transformer. v

The construction above described lends itself to convenient and economical manufacture in that ordinary pipes and. pipe fittings may be used for this part of the ap paratus.

When it becomes necessary to remove the cover of the transformer for repairs the operating mechanism of the tap changer may be disconnected by removing the bolt 20 between shaft 11 and insulator L0. The cover may then be removed without disturbing the contact-making apparatus. The arm 12 may also be disconnected from the shaft 11 by loosening'set screw 19. This is only necessary when repacking the acking box.

In some cases it may be d sirable to leave more room for the transformer leads, yet retain the advantages of double knife blade contacts, in which case the modified arrangement of the contact clips and switch arms 32-32 at an angle to eachother shown in Fig. 5 may be used. Only three pairs of contact clips 23-23, 24--24' and 25-25 are shown 1n this drawing, but any number maybe used depending on the electrical eonnections desired. As shown, diagrammatically the tap chan er is used to vary the number of turns 0 wire in the secondary coil, but it ma be used for other purposes requiring the c anging of connections inside the transformer case.

I claim:

1. The combination with a transformer and a tank containing the same, of contact makin means within said tank connected to a winding of said transformer, and means for operating said contact makzing means from outside of said tank, a packing means and a protecting hood for said packing means between said operating means and said packing means. I

2. The combination of a containin tank filled with oil, contact-making switch blades, clips for receiving said switch blades, external voperating and indexing means, and a connecting shaft provided with packin means for operating said switch blades an protected by a hood carried by said external operating means.

3. The combination of a tank containing oil, a suitably insulated shaft extending through the cover of said tank, packing means between said shaft and said cover constructed from cylindrical sections and protected on the outside of said cover by a cup ed hood mounted on said shaft, said sha t havin switch blades mounted thereon, aswitch sla within said tank provided with a series of contact clips designed to receive the switch blades, and means for indexing said switch blades preparatory to making contact with said contact clips.

4:. The combination with a tank containing oil of an insulated shaft extending through the cover of said tank, packing means between said shaft and said cover to prevent escape of the oil from said tank, an operating arm for said shaft provided with means for protecting said packing means from moisture, switch blades mounted on the inner end of said shaft within said tank, and a switch slab provided with contact members mounted within said tank for cooperation with said switch blades.

5. The combination with a tank containing oil of an insulated shaft extending through the cover of said tank, packing means between said shaft and said cover to prevent escape of the oil from said tank, an operating arm for said shaft provided with means for protecting said packing means from moisture, switch blades mounted on the inner end of said shaft within said tank, a switch slab provided with contact members mounted within said tank for cooperation with said switch blades, and indexing means between said arm and said cover.

6. The combination of a. transformer and enclosin casin having a cover, leads from the win ings oi said transformer, insulating supporting means in said casing below said cover, contacts carried by said means and connected to said leads, a rotatable and longitudinal moving shaft, the inner end of said shaft having a. connecting member for said contacts and journaled in said insulating supporting means in said casing, the

outer end passlng through and journaled in said cover, and operating means outside of said casing for rotatmg and shifting said shaft.

CLIFFORD A. ROBERTS. 

